Combo of burst wave lithotripsy and ultrasonic propulsion feasible for kidney stones

Combination treatment with burst wave lithotripsy (BWL) and ultrasonic propulsion for small, asymptomatic renal stones is feasible in an office-based setting with awake patients, according to findings presented on a poster at the 2024 AUA Annual Meeting.¹

Following this feasibility analysis, there is a second phase of the study with an additional 2 parts. Part A of the second phase will be a randomized controlled trial in all-comers, and Part B will be specifically focusing on patients with spinal cord injuries, according to study author Arturo Holmes, MD.

“BWL and ultrasonic propulsion may in the not-too-distant future offer a way to prophylactically remove small stones before they require an emergency department visit or surgery,” first study author Arturo Holmes MD, department of urology, UW medicine, Seattle Washington, and coauthors wrote in their poster conclusion.

The feasibility study recruited patients who had up to 3 kidney stones of 2 mm to 7 mm in size observed on CT within the previous 90 days. Patients were not eligible for enrollment if they had untreated infection or lacked the ability to hold anticoagulation.

All patients received transcutaneous ultrasound imaging with BWL to break stones and ultrasonic propulsion to reposition fragments. The treatment was administered in-office. Treatment exposure time was 30 minutes, with total procedure length varying based on physician’s experience and other factors. Patients were awake during the treatment and received continuous cardiac monitoring.

Pain assessments were conducted directly before and following the procedure and post-procedure urine samples were graded based on a published hematuria score (0-10). The study investigators asked participants to strain their urine and communicated with them weekly for 3 weeks for updates on fragment passage and potential adverse events (AEs).

The targeted enrollment for this ongoing feasibility assessment is 20 patients. There were 15 patients enrolled at the data cutoff for the findings shared at the AUA meeting. All 15 patients tolerated the procedure.

The primary outcome measure for the study was stone-free status on CT scan within 90 days post-procedure. Secondary outcome measures included change in stone volume, fragment passage, and AEs.

Thus far, 10 patients have received a <90 days CT and 4 are stone free. The median reduction in stone volume was 82% (interquartile ratio, 58-100).

Regarding safety, all AEs were mild in severity and resolved without any need for intervention. Among these AEs were instances of hematuria, renal colic, back pain, urinary urgency, and change in urinary frequency. There was 1 patient who had a history of urinary tract infections who received antibiotics following the procedure even though their urinalysis was negative.

Patient quality of life was also assessed using the Wisconsin Stone Quality of Life (WISQOL) questionnaire. Among 7 patients with complete responses, the average score before the procedure was 122 out of a maximum potential score of 140 (a higher score on WISQOL indicates a higher health-related quality of life). When presenting the findings at the AUA meeting, Holmes said that following the procedure, there was an “average increase in WISQOL score of 8.”

Following his presentation, an audience member asked Holmes if he and his fellow researchers analyzed the size of stone fragments found in the urine after the procedure.

“They were usually around 1 mm or so, a size at which you’re barely able to see them in the strainer,” Holmes responded.

Holmes was also asked about determinants of the total procedure length, beyond just the 30-minute period of the treatment itself.

“It’s user dependent, in terms of how well the user is able to utilize ultrasound to visualize the stones, especially because this is burst wave, not just propulsion, and so as you break the stone, it can become less visible; it goes from a single, hyperechoic area to kind of a dusty, clouded area,” explained Holmes.

Looking ahead, Holmes said that following this feasibility analysis, there is a second phase of the study with an additional 2 parts. Part A of the second phase will be a randomized controlled trial in all-comers, and Part B will be specifically focusing on patients with spinal cord injuries.

Reference

1. Holmes AE, Sorensen MD, Dunmire B, et al. Feasibility of burst wave lithotripsy and ultrasonic propulsion to expel small, asymptomatic, renal stones. Presented at: 2024 American Urological Association Annual Meeting. May 3-6, 2024, San Antonio, Texas. Abstract MP29-11.